Well they aren't diamond if they haven't done their placements. If you are referring to their last season placement then no that won't affect who you can team up with. Once they are placed it's a 1000 SR difference.
Yeah. Did the experiment once.
Played with a friend who had the bronze logo and I was doing my placements with Gm mmr. We were playing High Master/Low Gm games lmao
Lol unless the bronze is a smurf, they're just gonna lose every single game. They might get lucky once or twice though but that is a huge difference in skill my dude. Bronze is gonna have to get carried hard
There is a YouTube video of it, a silver did placements with a master. The prior season silver still placed in silver and the prior season master still placed master.